4.4. Peculiars and Mergers

The majority of the peculiars and interacting galaxies (UGC 05189, Arp 299, UGC 06527, UGC 08335, IC 2184, and Arp 239 [Section 3.33-3.38]) show a F300W morphology that is similar to that in F814W. Several mergers have spectacular dust-lanes that thread along with the spiral arms, which are tidally distorted during the interaction (UGC 08335; Arp 239), while most others have absorption in apparently random locations associated with a star-burst.

The HST images are in general not sufficiently deep nor do they sample a sufficiently large area on the sky to capture the lower SB features (e.g., low-SB tails and other large tidal features, faint extended disks or halos) that are well imaged on the ground-based photographic plates which were originally used to classify these objects. The inner regions of these objects reveal a wealth of structure in the HST images, but often are almost entirely burned out or blurred on these ground-based images. The HST images do thus not necessarily reflect the distribution of the extended (evolved) stellar population. This is particularly true of the interacting systems, where tidal forces first and most easily affect the outer regions of the participants. Because interacting galaxies have both a disturbed distribution of old stars in their outskirts and an irregular distribution of dust and young star-forming regions in their inner parts, their peculiar morphology is maintained over a range of spatial scales and surface brightnesses. As such, the morphological K-corrections derived from this sample mostly apply to the high-SB inner regions of these galaxies. However, these are the appropriate morphological K-corrections to be applied to studies of high-redshift galaxies, where cosmological SB-dimming similarly selects the high-SB regions as do our short HST exposures.

More statistics are needed to cover all late-types, and the major dynamical stages of peculiars and mergers, as these are likely the dominant population at high redshift. We will pursue such objects further through an HST SNAP-shot program of late-type/irregular and peculiar galaxies in Cycle 10.